Application Stack

 The Application Stack can be represented as a matrix that shows:

• the design tiers (layers) for the application, and for each application layer:
• the open standards selected, 
• the vendors and products blessed by the company (for volume purchase and training), 
• reusable components developed by the company, 
• the design and development tools used to model the design and generate/edit the source code and debug the application, and 
• the operational packages that administrate, monitor and manage the running application. 

Here is a partial example of an Application Stack. (This is just an example, not a recommendation.)  A column for reusable components should be added if this covers multiple applications in an enterprise.

Layer	Open Standard	Technology Stack	Dev. Tool	Operations Management
Communi-cation	TCP/IP, HTTP, HTML, SSL	Apache		Smarts, Remedy
Application	Java, J2EE	WebLogic, JSP, WDK	Eclipse	Smarts, JMX, Remedy
Data Access	XML, XML Schema	EJB, Documentum	SQLJ
Storage	Relational, SQL, XML	Oracle	ERwin	BMC
Operating System	Unix	Solaris	Tckl	Smarts
Security	LDAP	NDS, Netegrity

Here is another example (but its missing operations mgmt & reusable components): 

For multi-tier systems the applications layers are spread over multiple hardware systems, each with their own stack, with the application connected across systems by communication protocol stacks offering a wide array of features in support of the robustness of the application. This can be graphically represented as API stacks that abstract the hardware horizontally and the application over hardware nodes vertically. 

Here is an example of a 3-tiered application represented across the top of the stack and the hardware interfaces across the bottom of the stack. Thus this is not one stack but 3 stacks with the invocation and abstraction of the hardware going down the stack, while the transparent communication protocol is shown touching the relevant components between each stack: 

The SAN (XIOtech) could be broken out into a 4th tier if you wanted to be complete, after-all it does run in a separate system.